1. Field of the Invention
This invention relates to coated abrasive articles and, more particularly, to such articles which incorporate an energy cured hot melt make coat.
2. Description of the Related Art
Coated abrasive articles generally comprise a backing layer to which a multiplicity of abrasive particles are bonded. In one form, the abrasive particles are bonded to the backing by a first binder, commonly referred to as a make coat. A second binder, commonly called a size coat, is then applied over the make coat and the abrasive particles to reinforce the particles. In a second form, the abrasive particles are dispersed in a binder to provide an abrasive composite and the composite is bonded to the backing by the binder.
Porous cloth, fabric and textile materials are frequently used as backings for coated abrasive articles. The make coat is typically applied to the backing as a low viscosity material. In this condition, the make coat can migrate into the backing and accumulate in the interstices formed by the intersecting warp and fill fibers of the porous backing. This can result in the backing becoming stiff, hard and brittle with a consequent loss of its natural pliability. However, flexible, pliable, coated abrasive articles are desired. As a result, it has become conventional to employ a presize or saturant coat to seal the porous backing even though this added processing step increases the cost and complexity of manufacturing.
U.S. Pat. No. 4,163,647 "Method for Producing Coated Abrasives," issued Aug. 7, 1979 to H. J. Swiatek proposes coating a cloth backing material on its front side with a liquid thermosetting resin in such a manner that the resin does not permeate the interstices of the cloth. Suggested liquid thermosetting resins include heat hardenable phenol-formaldehydes.
U.S. Pat. No. 4,751,138 "Coated Abrasive Having Radiation Curable Binder," issued Jun. 14, 1988 to M. L. Tumey et al. discloses a radiation curable epoxy-based make coat. Reportedly, the radiation curable composition can be used to treat the backing material; for example, by saturating it or providing a front coat therefor.
U.S. Pat. No. 4,927,431 "Binder for Coated Abrasives," issued May 22, 1990 to S. J. Buchanan et al. discloses an abrasive product which utilizes a binder formed from a blend of a radiation curable monomer and a thermally curable resinous material. The binder bonds abrasive grains to a major surface of a backing sheet and can also function as a backing treatment for the coated abrasive article.
U.S. Pat. No. 4,240,807 "Substrate Having a Thermoplastic Binder Coating for Use in Fabricating Abrasive Sheets and Abrasive Sheets Manufactured Therewith," issued Dec. 23, 1980 to F. J. Kronzer discloses a flexible backing material which has a heat activated binder on one surface thereof. The binder is reportedly a nontacky solid at ambient temperatures, but when heated is converted to a viscous fluid that permits abrasive grains deposited thereon to sink into the coating to a depth which provides a firm bond therewith. When the heat is removed, the coating reverts to its solid nontacky state.
However, there remains considerable need for a make coat which can be readily applied to a porous cloth, fabric or textile backing without the need for a separate presize or saturant coat to seal the backing.